Protractors - Engineering & Drafting
By the end of the 18th century, protractors were routinely manufactured by machinery, with the invention of dividing engines, such as Jesse Ramsden's, particularly important for enabling the precise division of a circle into fractions of angles. Makers produced protractors that read minute fractions of angles, particularly when a vernier was added to the instrument.
Mechanics or machinists also used protractors to draw designs for new types of machinery. For instance, there were several forms of limb protractors for draftsmen that both functioned as T-squares and provided angle measurement. Similarly, protractors assisted with the preparation of architectural drawings. The instruments were only displaced by the advent of computer-aided drafting in the late 20th century.
"Protractors - Engineering & Drafting" showing 5 items.
Kern Semicircular Protractor
- Description
- This semicircular protractor is housed in its original wooden fitted case. The case is in very poor condition, but it was originally covered with thin leather and lined with purple velvet. The case is marked: I. KERN á AARAU [/] EN SUISSE. The maker’s mark indicates the protractor was produced between 1819 and 1885 in the workshop founded by Jakob Kern (1790–1867) in Aarau, Switzerland.
- Renamed Kern & Co. in 1885, the firm was highly regarded for its craftsmanship. Its products can be found in the catalogs of many 20th American manufacturers and retailers. Kern & Co. merged with the Wild Leitz group in 1988, and the plant in Aarau closed in 1991. Former employees ensured that 1,700 objects were preserved as the Kern Collection in the city museum of Aarau, Stadtmuseum Schlössli Aarau.
- The protractor is made of German silver, also called nickel silver. It is graduated along the outer edge to one-quarter degree and engraved by tens from 350 to 0 to 190 in both directions, from left to right and from right to left. A center cross-plate, or horncentre, contains crosshairs to assist with placing the protractor on a drawing. A movable arm attached to the center contains a vernier scale that allows the user to read angles to one minute of arc. The number 8 is stamped on the back of the vernier arm. The arm also has a blade-like extension three inches long. The arm was lengthened and squared off in versions sold in the 20th century. In 1909, Keuffel & Esser sold a similar protractor in a mahogany case for $19.25.
- This protractor was owned by the renowned American designer of steam engines, Erasmus Darwin Leavitt Jr. (1836–1916), and donated by his granddaughter, Margaret van D. Rice.
- See also ID numbers MA*247966 and 1978.2110.06.
- References: Juerg Dedual, “Milestones of Kern & Co. AG,” Virtual Archive of Wild Heerbrugg, http://www.wild-heerbrugg.com/Milestones%20of%20Kern.htm; “Kern & Co. Studiensammlung im Stadtmuseum Schlössli Aarau,” http://www.kern-aarau.ch; W. & L. E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying, 37th ed. (Troy, N.Y., 1903), 328–329; Catalogue of Keuffel & Esser Co. (New York, 1909), 170.
- Location
- Currently not on view
- date made
- 1819-1885
- maker
- Kern & Co.
- ID Number
- 1977.0460.02
- accession number
- 1977.0460
- catalog number
- 336073
- Data Source
- National Museum of American History, Kenneth E. Behring Center
Rectangular Protractor
- Description
- In the 18th and 19th centuries, draftsmen needed to prepare surveying and architectural drawings according to a variety of scales. Their work might call for them to reduce life-size conditions in a range from 1 inch to the foot to 1/8 inch to the foot. Draftsmen also needed a convenient way to keep all of the scales at hand without cluttering up their toolboxes with many drawing instruments. Instrument makers offered rectangular protractors as one tool to solve these problems.
- A rectangular protractor has the angle markings around three edges of a rectangle instead of along the arc of a circle or half-circle. The object looks like a ruler and fits neatly inside a pocket or a case of instruments. There is space in the interior of the rectangle—and on both sides—for other scales. Early rectangular protractors were often made of metals such as brass, but in the 19th century, makers manufactured large quantities of rectangular protractors from ivory.
- This ivory rectangular protractor typifies the general form of these instruments. It is graduated by single degrees and marked by tens from 10° to 170° in both directions, from left to right and from right to left. The front of the protractor also contains scales for 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8, and 1 inch to the foot, as well as a scale of chords. Draftsmen used a scale of chords together with compasses to draw arcs on which they could construct angles, particularly when a protractor was not available. This scale is divided by single degrees and marked from 10° to 90° by tens.
- The back of the protractor bears scales dividing the inch into 60, 50, 45, 40, 35, and 30 parts. These scales were also useful for creating and reading scale drawings. For instance, 1 inch on the 40 scale corresponded to 4 inches in real life, while 1 inch on the 60 scale corresponded to 6 inches in real life. Additionally, this protractor contains a diagonal scale, for reading off fractions of an inch, and a scale of cosines. John William Christopher Draper and James Christopher Draper of Pittsburgh donated this protractor to the Smithsonian in 1973.
- Reference: Amy Ackerberg-Hastings, "Rectangular Protractors and the Mathematics Classroom," in Hands on History: A Resource for Teaching Mathematics, edited by Amy Shell-Gellasch, MAA Notes no. 72 (Washington, DC: The Mathematical Association of America, 2007), 35–40.
- Location
- Currently not on view
- date made
- 19th century
- ID Number
- MA*335349
- accession number
- 304826
- catalog number
- 335349
- Data Source
- National Museum of American History, Kenneth E. Behring Center
Brown & Sharpe Draftsman's Protractor
- Description
- In the late 19th century, American draftsmen experimented with different designs for making protractors more versatile. For instance, the secretive machinist Samuel Darling, who operated a separate partnership with Joseph R. Brown and Lucian Sharpe of Providence, R.I., between 1866 and 1892, patented a "bevel and protractor" on July 19, 1887. This was a nearly circular protractor with an extended arm that slid along and rotated around a ruler.
- Alton J. Shaw, who apprenticed in the main firm of Brown & Sharpe, came up with a design that was less cumbersome than Darling's. Although Shaw filed for a patent one month before Darling did, Shaw's patent was not granted until August 2, 1887. His protractor consisted of a circle with an extending arm, cut from sheet steel, which fit on a groove within a three-sided square, also cut from sheet steel. An advantage of this protractor was its reversibility. Shaw assigned his patent to Darling, Brown, & Sharpe on August 19 in exchange for $75. The firm marketed the protractor for $6.50, or for $7.75 with a case. In its catalogs, Brown & Sharpe adopted the British spelling, "draughtsmen's".
- This instrument is an example of Shaw's design. The protractor is divided by single degrees and marked by fives from 0 to 90 in the clockwise direction. Thirty more unnumbered divisions extend past the 90° mark. A vernier on the frame allows angles to be measured to one minute of arc. The interior of the protractor is marked: Darling, Brown & Sharpe. (/) Providence. R.I. (/) Pat. Aug. 2. 1887. The protractor is in a wood and morocco leather case that is lined with purple velvet. The case has broken apart into at least three pieces. A worn instruction sheet (ID number MA*336072.1.1), dated August 1889, is stored with the object. The instructions indicate that a guiding lever, which was placed in two of the eleven holes at the top of the protracting circle, is missing from the object.
- Shaw later moved to Milwaukee, Wis., and then to Muskegon, Mich., where he established the Shaw Electric Crane Company. The company became Lift-Tech International in 1986. The Brown & Sharpe Mfg. Co. absorbed Darling, Brown & Sharpe in 1892. After over a century as one of the largest American machining firms, Brown & Sharpe ceased manufacturing machine tools and drawing instruments in 1991. The firm now manufactures optical measuring instruments as a subsidiary of Hexagon Metrology.
- This protractor was owned by the renowned American designer of steam engines, Erasmus Darwin Leavitt Jr. (1836–1916), and donated by his granddaughter, Margaret van D. Rice.
- See also ID number 1990.0317.02.
- References: Oscar James Beale, Practical Treatise on Gearing (Providence, R.I.: Brown & Sharpe Mfg. Co., 1886), 73-75; Samuel Darling, "Bevel and Protractor" (U.S. Patent 366,651 issued July 19, 1887); Alton J. Shaw, "Protractor" (U.S. Patent 367,673 issued August 2, 1887); Amy Ackerberg-Hastings, "The Brown & Sharpe Draftsmen's Protractor," Rittenhouse 15, no. 1 (2001): 31–38; Henry Dexter Sharpe, A Measure of Perfection: The History of Brown & Sharpe (North Kingston, R.I.: Brown & Sharpe, 1949), http://www.roseantiquetools.com/id44.html.
- Location
- Currently not on view
- date made
- 1889-1892
- patent date
- 1887
- maker
- Brown and Sharpe Manufacturing Company
- inventor
- Darling, Samuel
- ID Number
- 1977.0460.01
- accession number
- 1977.0460
- catalog number
- 336072
- Data Source
- National Museum of American History, Kenneth E. Behring Center
Brown & Sharpe Bevel Protractor
- Description
- This metal instrument consists of a circular protractor housed within an irregularly shaped blade. An 11-1/2" trapezoidal blade slides into the housing. A screw on the protractor fixes that blade in place. The protractor is divided by single degrees and marked by tens from 0° to 90° to 0° to 90° to 0°. A vernier, attached by another screw, permits angle readings to five minutes of accuracy. The protractor has a hinged case of leather over wood, lined with black satin. The case is gouged in several spots.
- Brown & Sharpe Manufacturing Co. introduced a "universal bevel protractor" in 1899, according to "Trade Notes," Science and Industry 4 (1899–1900): 274–275. Although there is no signature on this instrument, this protractor matches the illustrations in this article and in Brown & Sharpe catalogs at least as early as 1899 and at least as late as 1948.
- References: Kenneth L. Cope, intro., A Brown & Sharpe Catalogue Collection, 1868 to 1899 (Mendham, N.J.: The Astragal Press, 1997); Brown & Sharpe Mfg. Co., Small Tools: Catalog No. 27 (Providence, R.I., 1916), 92–93; The Brown & Sharpe Handbook: A Guide for Young Machinists (Providence, R.I., 1948), 49–54, 110–112.
- Location
- Currently not on view
- date made
- 1899-1949
- maker
- Brown and Sharpe Manufacturing Company
- ID Number
- 1986.0316.03
- accession number
- 1986.0316
- catalog number
- 1986.0316.03
- Data Source
- National Museum of American History, Kenneth E. Behring Center
Brown & Sharpe 510 Draftsman's Protractor
- Description
- See also ID number 1977.0460.01. After the inventor of this draftsman's protractor, Alton J. Shaw, left Darling, Brown & Sharpe of Providence, R.I., Samuel Darling patented a vernier scale that was a fraction of the size of a standard vernier scale. Darling then claimed to apply his vernier to the draftsman's protractor, replacing the original patent date in the maker's mark with the December 2, 1890, date of this patent. See, for example, the illustration in Brown & Sharpe's 1899 Catalogue No. 101 and Price Lists. This vernier read to only five minutes of accuracy, while Shaw's earlier vernier read to one minute of accuracy. Darling argued, however, that the coarser scale was easier to read and sufficed for most situations that arose in engineering drawing.
- In any event, the draftsman's protractor continued to sell steadily into the 20th century. Advertisements extolled the instrument's versatility, including its ability to function as a drawing triangle and as an extension of a T-square. The original patent date reappeared on the instrument in 1902 and 1904 but disappeared again by 1916, by which time Brown & Sharpe also changed the protractor's catalog number from 530 to 510. Other dealers, including Keuffel & Esser, W. & L. E. Gurley, and L. S. Starrett, also sold the draftsmen's protractor.
- The chief difference between this example of the instrument and ID number 1977.0460.01 is the reduced precision of the vernier, which is even marked: FIVE MINUTES. This protractor has 40 unmarked divisions, instead of 30. The signature is: 510; BROWN & SHARPE MFG. CO. (/) PROVIDENCE. R.I. U.S.A. The handle also bears the Brown & Sharpe logo of two rectangles at right angles to one another, with the letters B∙S above the horizontal rectangle and the words TRADE MARK below the horizontal rectangle. Of surviving 20th-century Brown & Sharpe catalogs, this protractor most closely resembles the illustration printed in 1925. The extending arm of the protractor is rusting.
- The protractor is stored in a blue paper box covered with the company logo and the words BROWN & SHARPE. A label on one end of the lid reads: 510; ORDER BY NUMBER 599-510 (/) BROWN & SHARPE DRAFTSMEN'S PROTRACTOR (/) MADE IN U.S.A. A label on the other end of the lid reads: POST (/) 0585 (/) THE FREDERICK POST CO. CHICAGO. Post retailed scientific and drawing instruments in the 20th century. An undated sheet with tables of angles for dividing circles and for tapers per foot is in the box.
- References: Samuel Darling, "Vernier-Scale" (U.S. Patent 442,020 issued December 2, 1890); Kenneth L. Cope, intro., A Brown & Sharpe Catalogue Collection, 1868 to 1899 (Mendham, N.J.: The Astragal Press, 1997); Brown & Sharpe Mfg. Co., Catalogue (Providence, R.I., 1902), 372; Brown & Sharpe Mfg. Co., Catalogue No. 138 (Providence, R.I., 1925), 504–505.
- Location
- Currently not on view
- date made
- ca 1925
- maker
- Brown and Sharpe Manufacturing Company
- ID Number
- 1990.0317.02
- accession number
- 1990.0317
- catalog number
- 1990.0317.02
- Data Source
- National Museum of American History, Kenneth E. Behring Center